A member for display device includes a color filter for use in a liquid crystal display device or the like. A typical example of the structure of a color filter for use in a liquid crystal display device will be described with reference to FIG. 1.
As shown in FIG. 1(a), a color liquid crystal display device (101) generally has a structure in which a color filter 1 and an electrode substrate 2 such as a TFT substrate are opposed to each other to provide a gap 3 of about 1 to 10 μm between them, the gap 3 is filled with a liquid crystal compound L, and the periphery thereof is sealed with a sealant 4. The color filter 1 has a structure in which a light-blocking layer (black matrix layer) 6 having a predetermined pattern for shielding a boundary region between pixels from light, a pixel part 7 for forming pixels of a plurality of colors (usually, three primary colors of red (R), green (G), and blue (B)) arranged in a predetermined order, a protective film 8, and a transparent electrode film 9 are laminated on a transparent substrate 5 in this order from the side close to the transparent substrate. On the inner side surface of each of the color filter 1 and the electrode substrate 2 opposed to the color filter 1, there is provided an orientation film 10. In addition, in the gap 3, there are provided spacers for keeping a cell gap between the color filter 1 and the electrode substrate 2 constant and uniform. As such spacers, pearls 11 having a constant particle diameter may be dispersed in the gap 3, or as shown in FIG. 1(b), column-shaped spacers 12 having a height corresponding to the cell gap may be formed on the inner side surface of the color filter and in a region overlapped on the position where the light-blocking layer 6 is formed. A color display image can be obtained by controlling the light transmittance of the colored pixels having their respective colors or the liquid crystal layer provided behind the color filter.
As described above, a color filter generally used has a light-blocking layer provided between pixels of red, green, and blue to block light. By providing such a light-blocking layer, it is possible to improve the contrast ratio between light and dark. As such a light-blocking layer, an inorganic light-blocking thin film such as a chromium single-layer thin film or a chromium/chromium oxide laminated thin film has been conventionally and widely used. However, the use of such an inorganic light-blocking thin film containing chromium as a light-blocking layer involves problems that a production cost becomes high due to the necessity of a vacuum process for forming the thin film and that waste adversely affects the environment.
In order to solve such problems, there is proposed a resin light-blocking layer obtained by dispersing light-blocking particles such as carbon black or titanium black in a resin. However, such a resin light-blocking layer has a problem that its optical density (OD value) per unit film thickness is smaller than that of the inorganic thin film light-blocking layer. For this reason, the resin light-blocking layer usually needs to have a thickness of 1 μm or more to increase the contrast between light and dark of a liquid crystal display panel to maintain its image quality high.
Recently, however, there is a demand for a thinner and higher-performance color filter, and therefore there is also a demand for a resin light-blocking layer which can maintain a high OD value even when the thickness thereof is reduced. Meanwhile, as shown in FIG. 2, a color filter usually used has a structure in which the pattern of the pixel film 7 partially overlaps the light-blocking layer 6. A level difference 22 between a pixel surface 20 and a top 21 of a part of the pixel film overlapping the light-blocking layer increases as the thickness of the light-blocking layer increases. If the level difference 22 is large, the alignment of a liquid crystal is disordered. For this reason, in the case of using a resin light-blocking layer as the light-blocking layer, a transparent planarization film called an overcoat is generally formed after the formation of the pixel film to reduce the level difference. However, the cost of forming the planarization film is becoming a big issue concerning the use of a resin light-blocking layer. Also for this reason, there is a demand for a resin light-blocking layer which can maintain a high OD value even when the thickness thereof is reduced.
In order to obtain a resin light-blocking layer which can maintain a high OD value even when the thickness thereof is reduced, for example, Patent Document 1 discloses the formation of a resin black matrix having an optical density per unit film thickness of 4.4/μm or more, a film thickness of 0.9 μm or less, and a surface roughness of 30 nm or more using a paste for resin black matrix containing graphite fine particles having an average particle diameter of 100 to 400 nm in an amount of 25 to 75 wt % of the total amount of components constituting the paste. However, graphite is a scale-like crystal, and therefore when the paste containing graphite particles as light-blocking particles is applied onto a substrate, each graphite crystal reflects incident light like a mirror surface so that there is a fear that a total reflectance is increased and therefore the contrast of a display device is reduced. For this reason, there is a demand for alternative light-blocking particles to graphite.
On the other hand, a resin light-blocking layer using titanium oxynitride particles obtained by replacing part of oxygen of titanium dioxide with nitrogen is mainly used as a high-resistance light-blocking layer. Among various such resin light-blocking layers, a resin light-blocking layer intended to achieve a high OD value is disclosed in, for example, Patent Document 2. The Patent Document 2 discloses the use of titanium oxynitride having the composition of TiNxOy (where 0<x<2.0 and 0.1<y<2.0) and produced by a method, in which titanium dioxide or titanium hydroxide is reduced at a high temperature in the presence of ammonia (Japanese Patent Application Laid-open (JP-A) Nos. 60-65069 and S61-201610), or a method, in which titanium dioxide or titanium hydroxide, to which a vanadium compound has been attached, is reduced at a high temperature in the presence of ammonia (JP-A No. 61-201610), in order to realize a resin black matrix formed from a black coating film having an optical density (OD value) of 3.0 or more per micrometer of film thickness and an adhesive strength of 5.0 MPa or more at the time when the contact area with glass is 5 mm2. Further, Patent Document 3 discloses a black coating composition containing, as essential components, titanium oxynitride and a resin and having an optical density (OD value) of 3.0 or more per micrometer of film thickness and an X-ray intensity ratio R of 0.24 or more, R being represented by the following formula (1) R=I3/[I3+1.8×(I1+1.8×I2)] (1), where I1 represents the maximum diffraction line intensity of the titanium oxynitride at a diffraction angle 2θ of 25° to 26°, I2 represents the maximum diffraction line intensity of the titanium oxynitride at a diffraction angle 2θ of 27° to 28°, and I3 represents the maximum diffraction line intensity of the titanium oxynitride at a diffraction angle 2θ of 36° to 38° in the case of using CuKα rays as an X-ray source. However, the titanium oxynitride described in the Patent Document 3 is based on the premise that the peak of anatase-type titanium dioxide appearing at a diffraction angle 2θ of 25 to 26° (Type A) or the peak of rutile-type titanium dioxide appearing at a diffraction angle 2θ of 27 to 28° (Type R) is present. That is, the titanium oxynitride described in the Patent Document 3 contains titanium dioxide remaining without being completely reduced to titanium oxynitride as I1 and I2 can be observed in the all of the Examples.
Patent Document 1: JP-A No. 2004-93656
Patent Document 2: JP-A No. 2004-4651
Patent Document 3: JP-A No. 2000-143985